The musculoskeletal system is subject to injury caused by traumatic events as well as by a number of diseases. Repair of connective tissue of the musculoskeletal system is commonly performed. By way of example, articular cartilage is a type of hyaline cartilage that lines the surfaces of the opposing bones in a diarthrodial joint (e.g., knee, hip, shoulder, etc.). Its primary function is to permit smooth, near frictionless movement during articulation between bones of the joint by providing a low-friction interface between the contacting cartilage surfaces of the joint. Articular cartilage is also load bearing, and serves to transmit and distribute compressive joint loads to the underlying subchondral bone.
Articular cartilage is typically damaged in one of two ways, acute trauma suffered through physical activity (such as twisting motion of the leg, sharp lateral motion of the knee, or repetitive impact), or degenerative conditions (such as arthritis or systemic conditions). In addition, as a person ages, articular cartilage loses mechanical strength, rendering the cartilage even more susceptible to trauma. Because articular cartilage tissue is aneural, i.e., having few or no nerves, and avascular, i.e., having few or no blood vessels, the healing of damaged cartilage is limited.
Consequently, various surgical methods are available for the treatment of damaged tissue, such as cartilage. In one treatment approach, the damaged tissue is removed and replaced with natural or synthetic materials that are physiologically acceptable to the human body and which perform the function formerly performed by the material removed. Recently, various orthopedic surgical procedures have replaced native tissue, such as cartilage, with a curable biocompatible material. Such surgical procedures have been performed using minimally invasive techniques, such as arthroscopic and endoscopic techniques, that allow as much of the healthy tissue as possible to remain. One type of biocompatible material that has shown promise for effecting soft tissue repair is hydrogels. Hydrogels are particularly suitable for minimally invasive procedures because they provide controllable phase change, such that the hydrogel may be injected through the minimally invasive device while in a liquid state and then cured in-situ to form a solid or a gel.
While the use of hydrogels has generally been successful to effect joint repair, their use does have some drawbacks. One such drawback is that while the hydrogel is in a liquid form, such as when delivering the hydrogel to a surgical site through the minimally invasive device, it has a relatively low viscosity. Consequently, the hydrogel flows easily and is therefore difficult to contain at the treatment site. Moreover, leakage of the hydrogel into or onto the tissue surrounding the surgical site may not be desirable in some surgical procedures. As a result, the use of hydrogels to effect joint repair has been heretofore limited.
Therefore, there is a need for improvements in a method and apparatus for delivering a biocompatible material to a surgical site.